Tag Archives: #nanotubes

Novel Compound Reveals Fundamental Properties of Smallest Carbon Nanotubes (Physics)

Chemical rings of carbon and hydrogen atoms curve to form relatively stable structures capable of conducting electricity and more — but how do these curved systems change when new components are introduced? Researchers based in Japan found that, with just a few sub-atomic additions, the properties can pivot to vary system states and behaviors, as demonstrated through a new synthesized chemical compound.

The results were published on April 26 in the Journal of the American Chemical Society.

“In the past decade, open-shell molecules have attracted considerable attention not only in the field of reactive intermediates, but also in materials science,” said paper author Manabu Abe, professor in the Graduate School of Advanced Science and Engineering, Hiroshima University.

Open-shell molecules can gain or lose molecules, meaning they can adjust to bond with other chemicals. In carbon nanotubes, for example, rings of carbon and hydrogen atoms strongly bond to one another. The more rings added, however, the more the properties of the tube can change. Known as curved paraphenylenes, or CPPs, Abe and his team investigated how the CPP might change if the open-shell molecules were exposed to systems with molecular orbits containing two electrons in various states, in addition to the carbon and hydrogen atoms.

The process of introducing these diradical systems to the CPPs resulted in a novel type of azoalkane, or compound of nitrogen and a group of weakly bonded hydrogen and carbon atoms. This azoalkane formed with six CPPs and degenerated into six CPPs with diradicals.

“We investigated to understand the effects of the curvature and system size on the particle interactions, the different states and their unique characteristics,” Abe said.

The researchers found that the CPPs with embedded diradicals had varying states and properties, such as the intrinsic description of a particle known as spin, depending on how many CPPs resulted in the final system. Spin, the angular momentum of a particle, can contribute to or hinder a system’s stability based on how the energy is balance. For example, in a singlet state, a system remains stable even with unbonded electrons, because their spins are opposite. Triplet states can remain stable, as well, since their unbonded electrons can spin in parallel.

“The ground-state spin multiplicity is largely dependent on the ring size,” Abe said, referring to the potential orientations spin can take, which can indicate the stability of a system. “The singlet ground state was favored for smaller CPP derivatives.”

The smaller singlet states — diradical CPPs with smaller energy ranges between orbital shells — also demonstrated a desired characteristic for carbon nanotubes: aromaticity, or more stable alignment in a single plane. Since the carbon-hydrogen rings bond with unusual angles to form the tubes, they can be forced out of alignment and result in system instability. The more rings added to a system, the more strained the system becomes. For the smaller singlet state systems, the rings align in one plane, resulting in more stability.

Next, the researchers plan to further investigate this in-plane aromaticity, with the aim of creating the largest possible structure with strong bonds that still exhibits this stable property.

Co-authors include Ivana Antol, Laboratory for Physical Organic Chemistry, Division of Organic Chemistry and Biochemistry, Ruder Bošvoíc Institute; Shigeru Yamago and Eiichi Kayahara, Institute for Chemical Research, Kyoto University; and Yuki Miyazawa, Zhe Wang, Misaki Matsumoto and Sayaka Hatano, Department of Chemistry, Graduate School of Advanced Science and Engineering, Hiroshima University.

Japan Society for the Promotion of Science, Japan Science and Technology Agency and International Collaborative Research Program of the Institute for Chemical Research at Kyoto University funded this work.

Featured image: The effects of the curvature contributes to their ground spin state. © Manabu Abe, Hiroshima University

Reference: Yuki Miyazawa, Zhe Wang, Misaki Matsumoto, Sayaka Hatano, Ivana Antol, Eiichi Kayahara, Shigeru Yamago, and Manabu Abe, “1,3-Diradicals Embedded in Curved Paraphenylene Units: Singlet versus Triplet State and In-Plane Aromaticity”, J. Am. Chem. Soc. 2021, 143, 19, 7426–7439.

Provided by Hiroshima University

On the New Character of Complexes of Fullerenes With Piperidine: Evidence of N→C Dative/Covalent Bond (Chemistry)

A team of researchers from the Pavel Hobza Group at IOCB Prague, Palacký University Olomouc (Czech Republic), and Luoyang Normal University (China) reported in Angewandte Chemie results of the combined experimental and computational studies on complexes formed between carbon allotropes (C20 and C60 fullerenes, graphene and single wall carbon nanotubes) and piperidine.

©IOCB pargue

Buckmisterfullerene C60, a widely known ball-shaped compound, and its derivatives attract the researcher’s attention due to their applications in bio-related and material-chemistry fields. The studies proved the existence of the unexpected N→C dative/covalent bond, formed solely in complexes of fullerenes with piperidine. Non-planarity and five-member rings of carbon allotropes represent the essential structural prerequisites for the unique formation of a dative N→C bond. The thermodynamics calculations, molecular dynamics simulations, and NMR and FT-IR spectroscopies explain the specific interactions between C60 and piperidine.

The differences in the behavior of individual carbon allotropes in terms of dative bonding formation brings new insight into their controllable organic functionalization. These results provide information about the reactivity-structure relations of carbon allotropes that are potentially useful for their simple and selective covalent functionalization, applicable to a broad portfolio of nanotechnologies.

New findings on the character of interaction of piperidine and other secondary amines with C60 are important for the rational design of modified fullerenes and their applications in electrocatalysis, spintronics, and energy storage.

References: Lamanec, M., Lo, R., Nachtigallová, D., Bakandritsos, A., Mohammadi, E., Dračínský, M., Zbořil, R., Hobza, P. and Wang, W. (2020), The Existence of a N→C Dative Bond in the C60–Piperidine Complex. Angew. Chem. Int. Ed. https://onlinelibrary.wiley.com/doi/10.1002/anie.202012851 https://doi.org/10.1002/anie.202012851

Provided by IOCB Pargue

Tiny Golden Bullets Could Help Tackle Asbestos-related Cancers (Medicine)

Gold nanotubes – tiny hollow cylinders one thousandth the width of a human hair – could be used to treat mesothelioma, a type of cancer caused by exposure to asbestos, according to a team of researchers at the Universities of Cambridge and Leeds.

Confocal fluorescence image of gold nanotures (green) in mesothelioma cells. ©Arsalan Azad.

In a study published today in journal Small, the researchers demonstrate that once inside the cancer cells, the nanotubes absorb light, causing them to heat up, thereby killing the cells.

More than 2,600 people are diagnosed in the UK each year with mesothelioma, a malignant form of cancer caused by exposure to asbestos. Although the use of asbestos is outlawed in the UK now, the country has the world’s highest levels of mesothelioma because it imported vast amounts of asbestos in the post-war years. The global usage of asbestos remains high, particularly in low- and middle-income countries, which means mesothelioma will become a global problem.

“Mesothelioma is one of the ‘hard-to-treat’ cancers, and the best we can offer people with existing treatments is a few months of extra survival,” said Dr Arsalan Azad from the Cambridge Institute for Medical Research at the University of Cambridge. “There’s an important unmet need for new, effective treatments.”

In 2018, the University of Cambridge was awarded £10million from the Engineering and Physical Sciences Research Council to help develop engineering solutions, including nanotech, to find ways to address hard-to-treat cancers.

In a collaboration between the University of Cambridge and University of Leeds, researchers have developed a form of gold nanotubes whose physical properties are ‘tunable’ – in other words, the team can tailor the wall thickness, microstructure, composition, and ability to absorb particular wavelengths of light.

The researchers added the nanotubes to mesothelioma cells cultured in the lab and found that they were absorbed by the cells, residing close to the nucleus, where the cell’s DNA lies. When the team targeted the cells with a laser, the nanotubes absorbed the light and heated up, killing the mesothelioma cell.

Professor Stefan Marciniak, also from the Cambridge Institute for Medical Research, added: “The mesothelioma cells ‘eat’ the nanotubes, leaving them susceptible when we shine light on them. Laser light is able to penetrate deep into tissue without causing damage to surrounding tissue. It then gets absorbed by the nanotubes, which heat up and, we hope in the future, could be used to cause localised cancer-cell killing.”

The team will be developing the work further to ensure the nanotubes are targeted to cancer cells with less effect on normal tissue.

The nanotubes are made in a two-step process. First, solid silver nanorods are created of the desired diameter. Gold is then deposited from solution onto the surface of the silver. As the gold builds-up at the surface, the silver dissolves from the inside to leave a hollow nanotube.

The approach advanced by the Leeds team allows these nanotubes to be developed at room temperature, which should make their manufacture at scale more feasible.

Professor Stephen Evans from the School of Physics and Astronomy at the University of Leeds said: “Having control over the size and shape of the nanotubes allows us to tune them to absorb light where the tissue is transparent and will allow them to be used for both the imaging and treatment of cancers. The next stage will be to load these nanotubes with medicines for enhanced therapies.”

References: Ye, S., Azad, A. A., Chambers, J. E., Beckett, A. J., Roach, L., Moorcroft, S. C. T., Aslam, Z., Prior, I. A., Markham, A. F., Coletta, P. L., Marciniak, S. J., Evans, S. D., Exploring High Aspect Ratio Gold Nanotubes as Cytosolic Agents: Structural Engineering and Uptake into Mesothelioma Cells. Small 2020, 2003793. https://doi.org/10.1002/smll.202003793

Provided by University of Cambridge

Researchers Develop Method For Earlier Detection Of Alzheimer’s Disease (Medicine)

Washington State University scientists have developed a method to detect the biomarkers for Alzheimer’s disease that is 10 times more sensitive than current blood testing technology.

A molecular-scale illustration of single-atom nanoyzmes and their application as a signal label in immunoassay. On the left, illustration of a protein biomarker being captured and detected in immunoassay. ©WSU

While still in the initial stages of development, the research could lead to earlier detection of the neurodegenerative brain disease that affects 5.8 million people in the U.S. That number is predicted to rise to 14 million Americans by 2050.

Led by Research Professor Dan (Annie) Du in WSU’s School of Mechanical and Materials Engineering, the researchers report on their work to use an artificial enzyme to detect the Alzheimer’s biomarkers in the Science partner journal, Research. WSU Ph.D. students Zhaoyuan Lyu and Shichao Ding are the co-first authors of the paper.

For Alzheimer’s disease, doctors most often diagnose patients based on their symptoms. By that time, the patients often already have severe brain damage. Imaging technology such as magnetic resonance imaging and CT scans can also be used to help confirm the disease, but they are not suitable for early stage diagnosis. Occasionally, doctors may test spinal fluid to look for beta-amyloid proteins, markers of the disease, but the process is more invasive than a simple blood test would be.

One common way of testing blood is the ELISA, or enzyme-linked immunosorbent assay, which is used to test for a variety of diseases such as HIV, which causes AIDS, and Lyme Disease. The ELISA uses a natural enzyme found in the roots of horseradish that can change color to indicate the presence of disease biomarkers. But, using the technique to detect the beta-amyloid proteins of Alzheimer’s is difficult because their levels in the blood are too small.

Last year, the WSU researchers created an artificial enzyme using a single-atom architecture that was able to work as efficiently as natural enzymes. Their artificial enzyme, called a nanozyme, is made of single iron atoms embedded in nitrogen-doped carbon nanotubes.

For this work, the researchers were able to use their single-atom nanozyme to mimic the active site of a natural enzyme and to detect the Alzheimer’s Disease proteins at levels 10 times lower than commercially available ELISA tests.

“The nanozyme based on a single-atom catalyst that we created has a similar structure as a natural enzyme with remarkable enzyme-like activity and paved the way for detecting the Alzheimer’s Disease biomarker,” Du said.

The nanozyme was also more robust than natural enzymes, which can degrade in acidic environments or in high temperatures. It is also less expensive and could be stored for long periods of time, Du added.

Lyu said she has family members who have been touched by Alzheimer’s Disease that has such a huge impact on the daily lives of patients and their families. She hopes that she can make a difference in detecting the disease earlier.

“This shows great potential for the early-stage diagnosis of Alzheimer’s Disease,” she said.

The next step of the research will involve testing their method with real blood samples.

In addition to the WSU team, scientists from Singapore helped to model the nanozyme’s structure, and Oregon State University and University of California researchers helped to characterize the single-atom catalysts.

References: Zhaoyuan Lyu, Shichao Ding, Nan Zhang, Yang Zhou, Nan Cheng, Maoyu Wang, Mingjie Xu, Zhenxing Feng, Xiangheng Niu, Yuan Cheng, Chao Zhang, Dan Du, Yuehe Lin, “Single-Atom Nanozymes Linked Immunosorbent Assay for Sensitive Detection of Aβ 1-40: A Biomarker of Alzheimer’s Disease”, Research, vol. 2020, Article ID 4724505, 11 pages, 2020. https://doi.org/10.34133/2020/4724505

Provided by Washington State University